LXR linux/arch/blackfin/include/asm/mutex.h

   1/*
   2 * Pull in the generic implementation for the mutex fastpath.
   3 *
   4 * TODO: implement optimized primitives instead, or leave the generic
   5 * implementation in place, or pick the atomic_xchg() based generic
   6 * implementation. (see asm-generic/mutex-xchg.h for details)
   7 *
   8 * Copyright 2006-2009 Analog Devices Inc.
   9 *
  10 * Licensed under the GPL-2 or later.
  11 */
  12
  13#ifndef _ASM_MUTEX_H
  14#define _ASM_MUTEX_H
  15
  16#ifndef CONFIG_SMP
  17#include <asm-generic/mutex.h>
  18#else
  19
  20static inline void
  21__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
  22{
  23        if (unlikely(atomic_dec_return(count) < 0))
  24                fail_fn(count);
  25        else
  26                smp_mb();
  27}
  28
  29static inline int
  30__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
  31{
  32        if (unlikely(atomic_dec_return(count) < 0))
  33                return fail_fn(count);
  34        else {
  35                smp_mb();
  36                return 0;
  37        }
  38}
  39
  40static inline void
  41__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
  42{
  43        smp_mb();
  44        if (unlikely(atomic_inc_return(count) <= 0))
  45                fail_fn(count);
  46}
  47
  48#define __mutex_slowpath_needs_to_unlock()              1
  49
  50static inline int
  51__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
  52{
  53        /*
  54         * We have two variants here. The cmpxchg based one is the best one
  55         * because it never induce a false contention state.  It is included
  56         * here because architectures using the inc/dec algorithms over the
  57         * xchg ones are much more likely to support cmpxchg natively.
  58         *
  59         * If not we fall back to the spinlock based variant - that is
  60         * just as efficient (and simpler) as a 'destructive' probing of
  61         * the mutex state would be.
  62         */
  63#ifdef __HAVE_ARCH_CMPXCHG
  64        if (likely(atomic_cmpxchg(count, 1, 0) == 1)) {
  65                smp_mb();
  66                return 1;
  67        }
  68        return 0;
  69#else
  70        return fail_fn(count);
  71#endif
  72}
  73
  74#endif
  75
  76#endif
  77